The present disclosure relates to a MTF measuring method for measuring MTF of a contact image sensor (CIS), and to a MTF adjusting method.
In recent years, CISs are often used in image reading apparatuses that are used in low-cost MFPs (Multi-Function Peripherals) or scanners. A CIS is an image reading sensor that includes a light source such as an LED or the like that irradiates light onto a document, multiple photoelectric conversion elements that are arranged in the main scanning direction of a CMOS sensor or the like (hereafter, referred to as a CMOS sensor), and a lens for directing light reflected from a document to the CMOS sensor. In addition, a CIS is mounted in a reading unit that moves back-and-forth in the sub scanning direction over the rear surface of a contact glass where a document is placed. As the reading unit moves, the CIS irradiates light toward the document, and receives incident reflected light from the document via the contact glass. In this way, the reading unit reads an image of the document.